Governmental regulations for automobile passenger restraint systems include an inflatable bag that momentarily and temporarily restrains a passenger during the critical instant of a collision impact. For safe and successful use the bag must be inflated in a very short time and thereafter deflated to release the passenger. The gas used to inflate the bag must be cool enough to avoid damage to the bag and injury to the passenger. Hot particles should be kept out of the bag. The inflation gas should also be non-toxic.
Some passenger restraint bags have been inflated with gas stored at high pressure and rapidly released into the bag. Another technique is to employ a gas generator having a solid composition which burns to produce substantial gas volumes. Preferably the combustion gasses produced are primarily carbon dioxide, water vapor, and oxygen, so that no toxic materials are released in the passenger compartment. It has been found that an excellent gas generation composition comprises about 1/4 or more anhydrous nickel formate and up to about 3/4 potassium chlorate. Such a composition burns evenly to produce large volumes of non-toxic gas. The net heat of reaction is low so that the gasses are not unduly hot as they enter the bag.
In manufacturing a gas generation composition the raw materials are preferably in powder form so that intimate mixture is obtained.
A gas generator for a passenger restraint system is installed when the automobile is manufactured and must remain ready for use throughout the life of the car. During this period it is subject to vibration and both high and low temperature extremes. Powders in a gas generator, therefore, may be undesirable because of potential segregation or packing due to vibration. It is also desirable to reduce dust problems when handling such compositions since the materials may be harmful and are combustible. A technique is therefore desirable for forming a propellant grain free of the problems of powders. Such a grain must have sufficient strength to withstand handling and long life in the gas generator.